Numerous devices are available for utilizing the flue gasses from a gas or oil fired forced air furnace in order to heat the area surrounding the flue or for heating a contiguous area. Most of these devices utilize some type of baffle arrangement which surrounds the flue in order to heat the air within same or some type of device which is insertable within the flue to heat the heating elements contained therein In addition, most of these devices include a blower apparatus to assist in the circulation of the air within the device and to direct the heated air to the area to be heated Thus, in general, all of these devices are directed to using the heat within the flue gasses for heating the area surrounding the flue or some other contiguous area.
The concept of preheating combustion air in order to conserve heating fuel, whether gas or oil, has been given some attention. The devices that are available, such as that disclosed in U.S. Pat. No. 4,167,212, are permanently mounted within the flue, have a relatively complex construction, and are quite expensive to produce Because of these limitations, these devices have not had wide commercial acceptance
In view of the foregoing, it has become desirable to develop a relatively simple, inexpensive heat exchanger device which is mountable within the flue of a gas or oil fired forced air furnace to recover the heat in the flue gasses passing therethrough, and which significantly reduces fuel usage by the furnace.